This invention relates to an apparatus for handling semiconductor wafers and positioning the wafers in front of an ion beam.
The onslaught of the computer age has brought an increasing need for semiconductor devices. Integrated circuits are made with semiconductors that have been doped with ions. To meet the increasing demand for doped semiconductors, the ion implantation of semiconductor wafers is performed by mass production. The semiconductor industry would benefit greatly by an increase in the thruput of wafers through an ion implantation process.
The doping of the wafers must take place within a vacuum. This presents one of the problems encountered in mass producing doped wafers. Time is often wasted by a depressurization step so that wafers can be passed from atomspheric pressure into a vacuum chamber. The repeated pumping down of the area surrounding a wafer before implantation slows the overall process.
One method known to the art for overcoming this difficulty is to have two locations where implantation takes place. A large and costly magnet system is used to switch the direction of the beam from one location to the other. In this approach while the beam is directed in one location the depressurization of the other location can take place. It would be desirable to eliminate the need for the large and costly magnet system.
Thruput can also be increased by increasing the intensity of the ion beam. This would reduce the amount of time necessary for the implantation step. However, the increase in power usage is inefficient and adds to the equipment cost. Also, the current expended during the time a wafer is being inserted into position for implantation is not put to a useful purpose. This current is wasted. It is the object of the present invention to reduce the amount of time required by the step of inserting a wafer into position for implantation, so that current is not wasted and thruput is increased.